This invention generally relates to a field of light emission device.
In FIG. 30, there is shown a conventional light emission device of a cannonball shape in which a chip of a light emitter (hereinafter called xe2x80x9clight emitterxe2x80x9d) 1 such as a light emitting diode (LED) or a semiconductor laser (LD) is mounted to be die-bonded on a lead frame 2, and electrically connected with another lead frame 3 by a bonding wire 4 to be sealed by a resin mold 6.
The conventional light emission device, however, is not considered about any heat dissipation structure other than the narrow lead frame 2 in order to radiate heat generated from the light emitter, thereby reducing the maximum rating current applied to the device due to damage by heat. Accordingly, as a larger current than the maximum rating current is applied for a long time period, a junction portion of the light emitter rises to a high temperature, thereby inviting characteristic deterioration or disconnection fault to decrease the reliability of the light emitter.
Depressing the maximum rating current causes a decrease in the quantity of light emission, whereby a large number of light emission devices must be employed to obtain a large quantity of light emission, which is uneconomical.
It is, therefore, a primary object of this invention to provide a light emission device having an improved heat dissipation performance in which the applicable maximum rating current is enlarged to emit light brightly, and characteristic deterioration by overheat of a light emitter or disconnection fault is prevented so as to improve the reliability of the light emitter.
It is another object of this invention to provide a light emission device array having excellent heat dissipation characteristics.
It is still another object of this invention to provide a light emission device having excellent heat dissipation characteristics in which a light emitter is of a surface mount type.
According to this invention, there is provided a light emission device including a light emitter and a light reflection member to emit light from the light emitter as generally parallel light from a front wall of the device, in which the light reflection member serves as a cooling plate to improve the heat dissipation performance.
According to a first aspect of this invention, there is provided a light emission device including a light emitter, a light reflection member and a resin sealing the light emitter by covering the light reflection member and the light emitter, in which light deviated from a predetermined front region in the light emitted from the light emitter is totally reflected by a boundary surface of the resin to be forwardly emitted by the light reflection member, and the light emitter is thermally contacted with the light reflection member to dissipate the heat generated from the light emitter.
The light reflection member serves as a heat dissipating plate by thermally contacting the light emitter with the light reflection member to increase the applicable maximum rating current by increasing the heat dissipation performance for bright light emission, thereby increasing the reliability of the light emitter by preventing characteristic deterioration by overheat of the light emitter or disconnection fault. The light emitter may be mounted on a lead frame electrically connected with the light emitter, which is thermally contacted with the light reflection member.
In order to improve the radiation characteristics, it is desirable to expose non-reflection surface of the light reflection member to air directly or through a thinned resin layer or cover a partial or whole surface of the resin by a peripheral edge of the light reflection member.
According to a second aspect of this invention, there is provided a light emission device including a light emitter, a light reflection member, a resin sealing the light emitter by covering the light reflection member and the light emitter, and a vertical plane body having good thermal conductivity, in which the light emitter is mounted on the vertical plane body and the vertical plane body is thermally connected with the light reflection member to dissipate heat of the light emitter through the vertical plane body and the light reflection member.
The vertical plane body is configured to have a dish portion on a center of the vertical plane body to be mounted by the light emitter, a groove for accommodating an insulator holding a lead frame, and a groove making the lead frame extending therethrough for easy assembling.
According to a third aspect of this invention, there is provided a light emission device including a light emitter mounted on a lead frame, a light reflection member, and a resin sealing the light emitter by covering the light reflection member and the light emitter, in which the light reflection member is formed with the lead frame as a single unit, thereby dissipating heat of the light emitter mounted on the lead frame through the light reflection member.
According to the second or third aspect of this invention, the lead frame or the vertical plane body having a good thermal conductivity is thermally contacted with the light reflection member, or the light reflection member is formed with the lead frame mounted by the light emitter as a single unit, thereby easily and firmly conveying the heat of the light emitter to the light reflection member for dissipation to increase the applicable maximum rating current for bright light emission and to further increase the reliability of the light emitter by preventing characteristic deterioration by overheat of the light emitter or disconnection fault.
According to a fourth aspect of this invention, there is provided a light emission device including a plurality of light reflection portions formed on a metal member in an array fashion, a plurality of light emitters each mounted near a center of each of the light reflection portions to be die-bonded, a wiring pattern disposed on a surface of the metal member through an insulation film to be connected with each of the light emitters, and a resin covering the light emitters above the light reflection portions, in which the resin is formed to direct light deviating from a predetermined front region about the light emitted from each of the light emitters to be substantially reflected at a boundary surface of the resin for forward emission by each of the light reflection portions, and heat generated from each of the light emitters is dissipated by the metal member.
Thus, a heat dissipation effect is provided by the metal member, thereby increasing the maximum rating current which can be applied to the light emitters for bright light emission, preventing a characteristic deterioration or any disconnection fault by overheat of the light emitters, whereby light emission device array having a high reliability may be provided.
According to a fifth aspect of this invention, there is provided a light emission device including an optical member having a light reflection member and a resin covering the light reflection member, and a light emitter of a surface mount type mounted on a metal plate, in which the resin is so constructed to direct light deviating from a predetermined front region about the light emitted from the light emitter to be substantially reflected at a boundary surface of the resin for forward emission by the light reflection member, and the light reflection member is thermally contacted with the metal plate to dissipate heat generated by the light emitter.
Thus, heat dissipation characteristics can be improved in the surface mount type light emission device, thereby increasing the maximum rating current which can be applied to the light emitter for bright light emission, preventing a characteristic deterioration or any disconnection fault by overheat of the light emitter, whereby the light emission device of the surface mount type having a high reliability may be provided.
Other objectives and advantages of this invention will be more readily apparent from the following detailed description provided in conjunction with the following figures.